US11070086B2 - Power receiving unit, power transmission system, and method of controlling the power receiving unit - Google Patents

Power receiving unit, power transmission system, and method of controlling the power receiving unit Download PDF

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Publication number
US11070086B2
US11070086B2 US15/902,395 US201815902395A US11070086B2 US 11070086 B2 US11070086 B2 US 11070086B2 US 201815902395 A US201815902395 A US 201815902395A US 11070086 B2 US11070086 B2 US 11070086B2
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power
coil
turns
converter
receiving unit
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US20180287427A1 (en
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Hirotaka Oshima
Kiyoto Matsui
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Fujitsu Ltd
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Fujitsu Ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J50/00—Circuit arrangements or systems for wireless supply or distribution of electric power
    • H02J50/40—Circuit arrangements or systems for wireless supply or distribution of electric power using two or more transmitting or receiving devices
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J50/00—Circuit arrangements or systems for wireless supply or distribution of electric power
    • H02J50/10—Circuit arrangements or systems for wireless supply or distribution of electric power using inductive coupling
    • H02J50/12—Circuit arrangements or systems for wireless supply or distribution of electric power using inductive coupling of the resonant type
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J50/00—Circuit arrangements or systems for wireless supply or distribution of electric power
    • H02J50/80—Circuit arrangements or systems for wireless supply or distribution of electric power involving the exchange of data, concerning supply or distribution of electric power, between transmitting devices and receiving devices
    • H02J7/025—
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac

Definitions

  • the embodiments discussed herein relate to a power receiving unit, a power transmission system, and a method of controlling the power receiving unit.
  • the contactless power receiving apparatus includes a resonance element to receive supply of alternating-current power in a contactless fashion by means of resonance from a resonance element of a power supplying source, an excitation element to receive supply of the alternating-current power by means of electromagnetic induction from the resonance element, a rectification circuit to generate and output direct-current power from the alternating-current power received by the excitation element, and a changeover circuit to change over the alternating-current power between a supplied state and a non-supplied state to the rectification circuit (see Patent Document 1, for example).
  • the contactless power receiving apparatus does not control an amount of electric power that is received from a power transmitting unit having the resonance element in the power supplying source, electric power cannot be transmitted effectively between the contactless power receiving apparatus and the power transmitting unit.
  • a power receiving unit includes: a secondary resonant coil configured to receive electric power from a primary resonant coil using magnetic resonance or electric field resonance occurring between the primary resonant coil and the secondary resonant coil, a secondary coil capable of changing a number of turns or a pitch of a winding configured to receive electric power from the secondary resonant coil using electromagnetic induction, a rectification circuit connected to an output side of the secondary coil configured to perform full-wave rectification of an alternating current power, a smoothing circuit connected to an output side of the rectification circuit, an output terminal for connecting an output side of the smoothing circuit with a DC-DC converter configured to supply electric power to a load circuit, and a controller configured to control the number of turns or the pitch of the winding of the secondary coil such that an input voltage of the DC-DC converter does not exceed an upper limit, based on a magnitude of the electric power received from the primary resonant coil.
  • FIG. 1 is a diagram illustrating a power transmission system
  • FIG. 2 is a diagram illustrating a power receiving unit and a power transmitting apparatus according to an embodiment
  • FIG. 3 is a diagram illustrating the power transmitting apparatus and electronic devices using a power transmission system according to the embodiment
  • FIG. 4 is a diagram illustrating a structure of a secondary coil
  • FIG. 5 is a diagram illustrating a structure of the secondary coil
  • FIGS. 6A, 6B, 6C, 7A and 7B illustrate states in which one or more power receiving units are receiving electric power from a primary resonant coil
  • FIG. 8 is a graph illustrating relation between a load resistance of a DC-DC converter and receiving power of the power receiving unit when the number of turns of the secondary coil is set to 1, 2, 3, 4, and 5;
  • FIG. 9 is a graph in which an input voltage of the DC-DC converter is added to the graph illustrated in FIG. 8 ;
  • FIG. 10 is a flowchart describing a process performed by a controller in the power receiving unit
  • FIG. 11 is a flowchart describing a process performed by a controller in a power transmitting unit
  • FIGS. 12 and 13 are diagrams illustrating a structure of a secondary coil according to a modified example of the embodiment.
  • FIG. 14 is a diagram illustrating a power receiving unit according to a modified example of the embodiment.
  • FIG. 1 is a diagram illustrating a power transmission system 50 .
  • the power transmission system 50 includes an alternating current power source (AC power source) 1 , a power transmitting unit 10 in a primary side (power transmitting side), and a power receiving unit 20 in a secondary side (power receiving side).
  • the power transmission system 50 may include multiple power transmitting units 10 or multiple power receiving units 20 .
  • the power transmitting unit 10 includes a primary coil 11 and a primary resonant coil 12 .
  • the power receiving unit 20 includes a secondary resonant coil 21 and a secondary coil 22 .
  • a load device 30 is connected to the secondary coil 22 .
  • the power transmitting unit 10 and the power receiving unit 20 transmit energy (electric power) from the power transmitting unit 10 to the power receiving unit 20 using magnetic resonance between the primary resonant coil 12 and the secondary resonant coil 21 .
  • Electric power can be transmitted from the primary resonant coil 12 to the secondary resonant coil 21 by not only using magnetic resonance, but also using electric field resonance. However, in the following description, power transmission using magnetic resonance will be mainly described.
  • a frequency of a voltage output by the AC power source 1 is 6.78 MHz
  • a resonant frequency of the primary resonant coil 12 and a resonant frequency of the secondary resonant coil 21 are 6.78 MHz.
  • Electromagnetic induction is also used for a power transmission from the secondary resonant coil 21 to the secondary coil 22 .
  • FIG. 2 is a diagram illustrating a power receiving unit 100 and a power transmitting apparatus 80 according to the present embodiment.
  • the power transmitting apparatus 80 includes an AC power source 1 and a power transmitting unit 300 .
  • the AC power source 1 is the same as that illustrated in FIG. 1 .
  • the power transmitting apparatus 80 includes the AC power source 1 and the power transmitting unit 300 .
  • the power transmitting unit 300 includes a primary coil 11 , a primary resonant coil 12 , a matching circuit 13 , a capacitor 14 , and a controller 310 .
  • the power receiving unit 100 includes a secondary resonant coil 110 , a secondary coil 120 , a rectification circuit 130 , a smoothing capacitor 140 , a controller 150 , a pair of output terminals 160 A and 160 B, a voltage detector 160 V, and an antenna 170 .
  • a DC-DC converter 210 is connected to the output terminals 160 A and 160 B.
  • a battery 220 is connected to an output of the DC-DC converter 210 .
  • FIG. 2 a case in which a load circuit is the battery 220 is illustrated.
  • the primary coil 11 is a loop shaped coil, and is connected to the AC power source 1 via the matching circuit 13 .
  • the primary coil 11 is disposed close to the primary resonant coil 12 in a noncontact manner, and is coupled to the primary resonant coil 12 electromagnetically.
  • the primary coil 11 is disposed such that a center axis of the primary coil 11 coincides with a center axis of the primary resonant coil 12 .
  • the reason the center axis of the primary coil 11 is made to coincide with a center axis of the primary resonant coil 12 is to improve a coupling strength between the primary coil 11 and the primary resonant coil 12 and to suppress occurrence of an unnecessary electromagnetic field around the primary coil 11 and the primary resonant coil 12 , by reducing leakage of magnetic flux.
  • the primary coil 11 produces a magnetic field using AC power supplied from the AC power source 1 via the matching circuit 13 , and transmits electric power to the primary resonant coil 12 using electromagnetic induction.
  • the primary coil 11 is disposed close to the primary resonant coil 12 in a noncontact manner, and is coupled to the primary resonant coil 12 electromagnetically.
  • the primary resonant coil 12 has a predetermined resonant frequency, and is designed to have a high Q factor.
  • the primary resonant coil 12 is designed to have the same resonant frequency as the resonant frequency of the secondary resonant coil 110 .
  • the capacitor 14 is connected to the primary resonant coil 12 such that each terminal of the capacitor 14 is respectively connected to a corresponding terminal of the primary resonant coil 12 to control the resonant frequency.
  • the primary resonant coil 12 is configured such that the resonant frequency is the same as a frequency of AC power output by the AC power source 1 .
  • the resonant frequency of the primary resonant coil 12 is determined by inductance of the primary resonant coil 12 and capacitance of the capacitor 14 . Therefore, the capacitance of the capacitor 14 is set such that the resonant frequency of the primary resonant coil 12 is the same as the frequency of the AC power output by the AC power source 1 .
  • the matching circuit 13 is disposed between the primary coil 11 and the AC power source 1 for impedance matching, and includes an inductor L and a capacitor C.
  • the AC power source 1 is a power source for outputting AC power having a frequency necessary for magnetic resonance, and includes an amplifier to amplify output power.
  • the AC power source 1 outputs, for example, AC power having a high frequency between hundreds of kilohertz and tens of megahertz.
  • the capacitor 14 is a variable capacitor. Each terminal of the capacitor 14 is respectively connected to the corresponding terminal of the primary resonant coil 12 .
  • the capacitor 14 is provided to control the resonant frequency of the primary resonant coil 12 , and the capacitance of the capacitor 14 is set by the controller 310 .
  • the controller 310 controls an output voltage and an output frequency of the AC power source 1 , capacitance of the capacitor 14 , a magnitude of electric power output from the primary resonant coil 12 , and the like.
  • the above described power transmitting apparatus 80 transmits electric power supplied to the primary coil 11 from the AC power source 1 , to the primary resonant coil 12 using electromagnetic induction, and transmits the electric power from the primary resonant coil 12 to the secondary resonant coil 110 of the power receiving unit 100 using magnetic resonance.
  • the secondary resonant coil 110 has a same resonant frequency as the resonant frequency of the primary resonant coil 12 , and is designed to have a high Q factor. A pair of terminals of the secondary resonant coil 110 is connected to a capacitor 111 .
  • the secondary resonant coil 110 is coupled to the secondary coil 120 electromagnetically, and transmits electric power to the secondary coil 120 using electromagnetic induction.
  • the secondary resonant coil 110 transmits electric power, which is received from the primary resonant coil 12 of the power transmitting unit 300 using magnetic resonance, to the secondary coil 120 using electromagnetic induction.
  • the secondary resonant coil 110 corresponds to the secondary resonant coil 21 illustrated in FIG. 1 .
  • the secondary coil 120 is configured such that the number of turns of a winding is variable.
  • a pair of terminals of the secondary coil 120 is connected to the rectification circuit 130 .
  • the secondary coil 120 outputs electric power, received from the secondary resonant coil 110 using electromagnetic induction, to the rectification circuit 130 .
  • the reason the number of turns of the secondary coil 120 is variable is to make output voltage of the secondary coil 120 variable and to make input voltage of the DC-DC converter 210 variable.
  • the output voltage of the secondary coil 120 can be changed in accordance with the number of turns of the secondary coil 120 . Further, making the input voltage of the DC-DC converter 210 variable is equivalent to making a load resistance of the DC-DC converter 210 as seen by input terminals 211 A and 211 B variable.
  • the rectification circuit 130 includes four diodes 131 A, 131 B, 131 C, and 131 D.
  • the diodes 131 A to 131 D are connected in a bridge configuration.
  • the electric power input from the secondary coil 120 is full-wave rectified by the diodes 131 A to 131 D, and the rectification circuit 130 outputs the full-wave rectified electric power.
  • the smoothing capacitor 140 is connected to an output side of the rectification circuit 130 , and smooths the electric power, which was full-wave rectified at the rectification circuit 130 , to output direct current power (DC power).
  • the output terminals 160 A and 160 B are connected to an output side of the smoothing capacitor 140 . Since the negative half of the waveform of the AC power input to the rectification circuit 130 is inverted, the electric power which was full-wave rectified at the rectification circuit 130 can be treated as DC power substantially. However, even for a case of the full-wave rectified electric power including ripples, steady DC power can be obtained by using the smoothing capacitor 140 .
  • the controller 150 includes a memory 150 M.
  • the controller 150 controls the number of turns of the secondary coil 120 .
  • the controller 150 sends data indicating that the number of turns has been changed to the power transmitting unit 300 via the antenna 170 .
  • the controller 150 receives a signal representing an amount of voltage detected by the voltage detector 160 V.
  • the controller 150 detects state of charge of the battery 220 .
  • the antenna 170 is connected to the controller 150 .
  • the antenna 170 is used for wireless communication with the power transmitting unit 300 . Note that the controller 150 and the antenna 170 are an example of a receiving side communication unit.
  • the voltage detector 160 V is for detecting a voltage across the output terminals 160 A and 160 B, and each terminal of the voltage detector 160 V is respectively connected to the output terminals 160 A and 160 B.
  • the voltage detector 160 V inputs a signal representing an amount of the detected voltage to the controller 150 .
  • the voltage (voltage across the output terminals 160 A and 160 B) detected by the voltage detector 160 V is an input voltage of the DC-DC converter 210 .
  • the DC-DC converter 210 includes the input terminals 211 A and 211 B, which are respectively connected to the output terminals 160 A and 160 B.
  • the DC-DC converter 210 converts a DC voltage output by the power receiving unit 100 into a rated voltage of the battery 220 .
  • the voltage across the input terminals 211 A and 211 B (or the voltage across the output terminals 160 A and 160 B) is an input voltage of the DC-DC converter 210 .
  • the DC-DC converter 210 is, for example, a step-down DC-DC converter, and lowers an input voltage (a voltage of an electric power supplied via the rectification circuit 130 ) to the rated voltage of the battery 220 . Because a step-down DC-DC converter is low-current and compact as compared to a step-up DC-DC converter or a step-up/down DC-DC converter, the step-down DC-DC converter is suitable for the power receiving unit 100 which is required to be compact. Therefore, it is preferable that the step-down DC-DC converter is used as the DC-DC converter 210 .
  • the load resistance of the DC-DC converter 210 as seen by the input terminals 211 A and 211 B varies in accordance with step-down control of voltage.
  • the input voltage of the DC-DC converter 210 also varies.
  • the power receiving unit 100 controls the output voltage of the secondary coil 120 by changing the number of turns, so that variation of the input voltage of the DC-DC converter 210 is within a predetermined range.
  • the load resistance of the DC-DC converter 210 is resistance of a load circuit (on the battery 220 side) as seen by the input terminals 211 A and 211 B.
  • the predetermined range of the input voltage of the DC-DC converter 210 is a range of not less than a lower limit of the input voltage and not more than an upper limit of the input voltage.
  • the lower limit of the input voltage is a minimum input voltage for the DC-DC converter 210 to operate normally. If the input voltage is lower than the lower limit, the DC-DC converter 210 cannot perform step-down control, and stops operation.
  • the upper limit of the input voltage is a maximum voltage for the DC-DC converter 210 that is allowed to be input. If the input voltage exceeds the upper limit, the DC-DC converter 210 stops operation because there is a risk that the DC-DC converter 210 may be damaged.
  • the battery 220 is a secondary cell which is a rechargeable battery.
  • a lithium-ion rechargeable battery can be used as the battery 220 .
  • the battery 220 is a main battery of such an electronic device.
  • the battery 220 outputs data representing the state of charge to the controller 150 . By receiving the data, the controller 150 can recognize the state of charge of the battery 220 , and can determine if the battery 220 is fully charged.
  • the primary coil 11 , the primary resonant coil 12 , and the secondary resonant coil 110 are formed by coiling a copper wire.
  • metals other than copper such as gold or aluminum
  • a material of each of the primary coil 11 , the primary resonant coil 12 , and the secondary resonant coil 110 may differ.
  • the primary coil 11 and the primary resonant coil 12 correspond to a power transmitting side
  • the secondary resonant coil 110 corresponds to a power receiving side
  • electric power is transmitted from the power transmitting side to the power receiving side using magnetic resonance generated between the primary resonant coil 12 and the secondary resonant coil 110 (magnetic resonance system)
  • electric power can be transmitted over a longer distance than an electromagnetic induction system to transmit electric power from the power transmitting side to the power receiving side using electromagnetic induction.
  • the magnetic resonance system Since the magnetic resonance system is more flexible than the electromagnetic induction system with respect to a distance or a position gap between resonant coils, the magnetic resonance system has an advantage called “free-positioning”.
  • FIG. 3 is a diagram illustrating the power transmitting apparatus 80 and electronic devices 200 A and 200 B using a power transmission system 500 according to the present embodiment.
  • the power transmitting apparatus 80 is the same as the power transmitting apparatus 80 illustrated in FIG. 2 . However, in FIG. 3 , components of the power transmitting apparatus 80 illustrated in FIG. 2 , other than the primary resonant coil 12 and the controller 310 , are illustrated as a power unit 10 A.
  • the power unit 10 A denotes a set of the primary coil 11 , the matching circuit 13 , and the capacitor 14 .
  • a set of the AC power source 1 , the primary coil 11 , the matching circuit 13 , and the capacitor 14 may be regarded as a power unit.
  • the power transmitting apparatus 80 also includes an antenna 16 .
  • the antenna 16 may be an antenna which can be used for a short-range wireless communication such as Bluetooth (Registered Trademark).
  • the power transmitting apparatus 80 includes the antenna 16 to receive, from a power receiving unit 100 A included in the electronic device 200 A (or a power receiving unit 100 B included in the electronic device 200 B), data indicating that, for example, the number of turns of a secondary coil 120 A (or 120 B) is changed.
  • the received data is entered to the controller 310 .
  • the controller 310 and the antenna 16 are an example of a transmitting side communication unit.
  • Each of the electronic devices 200 A and 200 B is, for example, a terminal such as a tablet computer or a smartphone.
  • the electronic device 200 A includes the power receiving unit 100 A, a DC-DC converter 210 A and a battery 220 A.
  • the electronic device 200 B includes the power receiving unit 100 B, a DC-DC converter 210 B and a battery 220 B.
  • the power receiving units 100 A and 100 B are configured with respectively designating an antenna 170 A and an antenna 170 B with respect to the power receiving unit 100 illustrated in FIG. 2 .
  • Each of the DC-DC converters 210 A and 210 B is the same as the DC-DC converter 210 illustrated in FIG. 2 (Note that the DC-DC converter is described as a “DCDC” in FIG. 3 ).
  • Each of the batteries 220 A and 220 B is also the same as the battery 220 illustrated in FIG. 2 .
  • the power receiving unit 100 A includes a secondary resonant coil 110 A, a secondary coil 120 A, a rectification circuit 130 A, a smoothing capacitor 140 A, a controller 150 A, and an antenna 170 A.
  • the secondary resonant coil 110 A, the secondary coil 120 A, the rectification circuit 130 A, the smoothing capacitor 140 A, and the controller 150 A respectively correspond to the secondary resonant coil 110 , the secondary coil 120 , the rectification circuit 130 , the smoothing capacitor 140 , and the controller 150 , illustrated in FIG. 2 .
  • each of the secondary resonant coil 110 A, the secondary coil 120 A, the rectification circuit 130 A, and the smoothing capacitor 140 A is illustrated in a simplified manner in FIG. 3 . Also, illustration of the output terminals 160 A and 160 B and the voltage detector 160 V is omitted in FIG. 3 .
  • the power receiving unit 100 B includes a secondary resonant coil 110 B, a secondary coil 120 B, a rectification circuit 130 B, a smoothing capacitor 140 B, a controller 150 B, and an antenna 170 B.
  • the secondary resonant coil 110 B, the secondary coil 120 B, the rectification circuit 130 B, the smoothing capacitor 140 B, and the controller 150 B respectively correspond to the secondary resonant coil 110 , the secondary coil 120 , the rectification circuit 130 , the smoothing capacitor 140 , and the controller 150 , illustrated in FIG. 2 .
  • each of the secondary resonant coil 110 B, the secondary coil 120 B, the rectification circuit 130 B, and the smoothing capacitor 140 B is illustrated in a simplified manner in FIG. 3 . Also, illustration of the output terminals 160 A and 160 B and the voltage detector 160 V is omitted in FIG. 3 .
  • the antennas 170 A and 170 B may be an antenna which can be used for a short-range wireless communication such as Bluetooth (Registered Trademark).
  • the power receiving units 100 A and 100 B respectively include the antennas 170 A and 170 B to perform data communication with the power transmitting unit 300 , and are respectively connected to the controller 150 A in the power receiving unit 100 A and the controller 150 B in the power receiving unit 100 B.
  • the controller 150 A in the power receiving unit 100 A sends data indicating that, for example, the number of turns of a secondary coil 120 A is changed, to the power transmitting unit 300 via the antenna 170 A.
  • the controller 150 B in the power receiving unit 100 B sends data indicating that, for example, the number of turns of a secondary coil 120 B is changed, to the power transmitting unit 300 via the antenna 170 B.
  • the electronic devices 200 A and 200 B can charge the batteries 220 A and 220 B respectively without contact with the power transmitting apparatus 80 , by simply placing the electronic devices 200 A and 200 B near the power transmitting apparatus 80 .
  • the batteries 220 A and 220 B can be charged simultaneously.
  • the power transmission system 500 is configured by the power transmitting unit 300 , the power receiving unit 100 A, and the power receiving unit 100 B. That is, the power transmitting apparatus 80 , the electronic devices 200 A and 200 B are using the power transmission system 500 realizing a contactless electric power transmission using magnetic resonance.
  • FIGS. 4 and 5 are diagrams illustrating a structure of the secondary coil 120 .
  • the secondary coil 120 includes a pair of terminals 121 A and 121 B, and a winding (metal wire) from the terminal 121 A to the terminal 121 B is coiled spirally.
  • the terminals 121 A and 121 B are on a line R 1 passing through to a center 122 of the secondary coil 120 .
  • the winding of the secondary coil 120 is spirally wound 5 times at constant spacing from the terminal 121 A to the terminal 121 B.
  • the secondary coil 120 also includes terminals 123 A, 123 B, 123 C, and 123 D located on the line passing through the terminals 121 A and 121 B and to the center 122 .
  • the terminals 123 A, 123 B, 123 C, and 123 D are on the line R 1 between the terminal 121 A and the terminal 121 B, in an order of the terminals 123 A, 123 B, 123 C, and 123 D.
  • the secondary coil 120 further includes a switch 124 , and terminals 125 A and 125 B.
  • the switch 124 includes switch units 124 A, 124 B, 124 C, 124 D, and 124 E.
  • the switch units 124 A, 124 B, 124 C, 124 D, and 124 E are respectively connected at one end to the terminals 123 A, 123 B, 123 C, 123 D, and 121 B, and are each connected at the other end to the terminal 125 B. Further, the terminal 125 A is connected to the terminal 121 A.
  • the switch unit 124 E As illustrated in FIG. 4 , if the switch unit 124 E is closed (is turned on), and the switch units 124 A, 124 B, 124 C, and 124 D are opened (are turned off), the secondary coil 120 becomes a 5-turn coil from the terminal 121 A to the terminal 121 B.
  • the switch unit 124 C As illustrated in FIG. 5 , if the switch unit 124 C is closed (is turned on), and the switch units 124 A, 124 B, 124 D, and 124 E are opened (are turned off), the secondary coil 120 becomes a 3-turn coil from the terminal 121 A to the terminal 123 C.
  • the switch unit 124 A is closed (is turned on), and the switch units 124 B, 124 C, 124 D, and 124 E are opened (are turned off), the secondary coil 120 becomes a 1-turn coil from the terminal 121 A to the terminal 123 A. If the switch unit 124 B is closed (is turned on), and the switch units 124 A, 124 C, 124 D, and 124 E are opened (are turned off), the secondary coil 120 becomes a 2-turn coil from the terminal 121 A to the terminal 123 B.
  • the switch unit 124 D is closed (is turned on), and the switch units 124 A, 124 B, 124 C, and 124 E are opened (are turned off), the secondary coil 120 becomes a 4-turn coil from the terminal 121 A to the terminal 123 D.
  • the switch units 124 A, 124 B, 124 C, 124 D, and 124 E By selecting any one of the switch units 124 A, 124 B, 124 C, 124 D, and 124 E and closing (turning on) the selected switch unit, the number of turns of the secondary coil 120 can be changed.
  • On/off control of the switch units 124 A, 124 B, 124 C, 124 D, and 124 E in the switch 124 is performed by the controller 150 .
  • the on/off control of the switch units 124 A, 124 B, 124 C, 124 D, and 124 E is referred to as “on/off control of the switch 124 ”.
  • the controller 150 can change output voltage of the secondary coil 120 .
  • the output voltage of the secondary coil 120 is changed, the input voltage of the DC-DC converter 210 and a load resistance are also changed.
  • FIGS. 6 and 7 illustrate states in which the power receiving unit 100 A is receiving electric power (or the power receiving units 100 A and 100 B are receiving electric power) from the primary resonant coil 12 .
  • the power receiving units 100 A and 100 B are illustrated in a simplified manner in FIGS. 6 and 7 .
  • the power receiving unit 100 A is represented as a set of two coils corresponding to the secondary resonant coil 110 A and the secondary coil 120 A
  • the power receiving unit 100 B is represented as a set of two coils corresponding to the secondary resonant coil 110 B and the secondary coil 120 B.
  • the power receiving unit 100 A may be configured such that only the power receiving unit 100 A can receive electric power most effectively.
  • the power receiving unit 100 A can receive electric power most effectively when the number of turns of the secondary coil 120 A is 3. Also in this case, let the power received by the power receiving unit 100 A be P 1 , and let the input voltage of the DC-DC converter 210 A be Vin 1 .
  • the power transmitting apparatus 80 increases the transmitting power.
  • the DC-DC converter 210 A of the power receiving unit 100 A increases the load resistance such that the receiving power does not change from the state when only the power receiving unit 100 A was receiving the electric power.
  • the power received by the power receiving unit 100 A and the input voltage of the DC-DC converter 210 A in a state illustrated in FIG. 6B are referred to as P 2 and Vin 2 respectively. Because the power receiving unit 100 A charges the battery 220 A (see FIG. 3 ) by receiving the same electric power as the state in FIG. 6A , P 2 is equal to P 1 , which is the power received by the power receiving unit 100 A in a state illustrated in FIG. 6A .
  • Vin 2 With respect to Vin 2 , because P 2 is equal to P 1 and the load resistance of the DC-DC converter 210 A becomes larger, Vin 2 (the input voltage of the DC-DC converter 210 A) becomes larger than Vin 1 .
  • the power receiving unit 100 A decreases the number of turns of the secondary coil 120 A to reduce Vin 2 .
  • the number of turns of the secondary coil 120 A is reduced to two in a state illustrated in FIG. 6C .
  • the input voltage of the DC-DC converter 210 A (referred to as “Vin 3 ”) in the state illustrated in FIG. 6C becomes less than Vin 2 .
  • the power received by the power receiving unit 100 A in the state in FIG. 6C (referred to as “P 3 ”) is equal to P 2 (or P 1 ), the load resistance also decreases.
  • the input voltage of the DC-DC converter 210 A can be controlled so as not to exceed the upper limit.
  • FIG. 7A illustrates a state in which the power receiving units 100 A and 100 B are receiving electric power from the primary resonant coil 12 and the number of turns of the secondary coils 120 A and 120 B are respectively set to 2 and 3 that are the optimal numbers for the secondary coils 120 A and 120 B. If the number of turns of the secondary coils 120 A and 120 B are optimal for both, the power receiving units 100 A and 100 B can continue receiving power without changing the number of turns of the secondary coils 120 A and 120 B.
  • FIG. 7B also illustrates a state in which the power receiving units 100 A and 100 B are receiving electric power from the primary resonant coil 12 .
  • the number of turns of both the secondary coils 120 A and 120 B are reduced to 2 because the transmitting power is in excess. If the number of turns is reduced as illustrated here, the power transmitting unit 300 reduces the transmitting power.
  • the power transmitting unit 300 stops reducing the transmitting power. For example, when the state of the power receiving units are such that the number of turns of the secondary coils 120 A and 120 B are reduced to 2 as illustrated in FIG. 7B , if the power receiving unit 100 B returns the number of turns to 3, the power transmitting unit 300 stops reducing the transmitting power.
  • FIG. 8 is a graph illustrating a relation between the load resistance of the DC-DC converter 210 and the receiving power of the power receiving unit 100 , when the number of turns of the secondary coil 120 is set to 1, 2, 3, 4, and 5.
  • a horizontal axis represents the load resistance of the DC-DC converter 210
  • a vertical axis represents the normalized receiving power of the power receiving unit 100 . Note that a receiving voltage of the power receiving unit 100 is constant.
  • the resonant state between the primary resonant coil 12 and the secondary coil 120 is changed.
  • the load resistance at which the receiving power is maximized changes.
  • characteristics curves of the receiving power shift to the right (to the direction of higher resistance) in the graph.
  • the load resistance is 26 ⁇ .
  • the load resistance is 11 ⁇ .
  • the load resistance can be changed by changing the number of turns. If the number of turns is reduced, the load resistance becomes lower.
  • two load resistance values may be present to attain desired receiving power.
  • the load resistance is 26 ⁇ or 11 ⁇ .
  • the load resistance is 11 ⁇ or 2.5 ⁇ .
  • the load resistance higher than the load resistance corresponding to a peak of the receiving power (a load resistance when the electric power received from the primary resonant coil is maximum) is adopted (26 ⁇ and 11 ⁇ in the above cases).
  • the DC-DC converter 210 is a step-down DC-DC converter, when the load resistance is smaller than a load resistance corresponding to a peak of the receiving power, the input voltage to attain the desired receiving power may be smaller than the lower limit.
  • FIG. 9 is a graph in which the input voltage of the DC-DC converter 210 (Vin) is added to the graph illustrated in FIG. 8 . Note that values of the input voltage Vin illustrated in FIG. 9 are normalized values.
  • the receiving power P does not change before and after changing the number of turns of the secondary coil 120 .
  • the load resistance is 45 ⁇ . Further, if the number of turns of the secondary coil 120 is 3, the load resistance is 26 ⁇ . Further, if the number of turns of the secondary coil 120 is 2, the load resistance is 11 ⁇ , and if the number of turns of the secondary coil 120 is 1, the load resistance is 2.2 ⁇ .
  • the input voltage of the DC-DC converter 210 (Vin) and the number of turns of the secondary coil 120 are in the following relation: If the number of turns of the secondary coil 120 is 4, the input voltage Vin is 1.8. If the number of turns of the secondary coil 120 is 3, the input voltage Vin is 1.4. If the number of turns of the secondary coil 120 is 2, the input voltage Vin is 0.9. And, if the number of turns of the secondary coil 120 is 1, the input voltage Vin is 0.4. That is, when the number of turns is reduced, the input voltage can be reduced.
  • the number of turns of the secondary coil 120 should be decreased to 2.
  • the power receiving unit 100 should maintain data representing the relation between the load resistance of the DC-DC converter 210 and the receiving power of the power receiving unit 100 for each number of turns of the secondary coil 120 , as illustrated in FIG. 8 or FIG. 9 , in the memory 150 M of the controller 150 .
  • FIG. 10 is a flowchart describing the process performed by the controller 150 in the power receiving unit 100 .
  • the flowchart illustrated in FIG. 10 represents a method for controlling the power receiving unit 100 .
  • the process is started.
  • the number of turns of the secondary coil 120 of the power receiving unit 100 is set to the optimal value in a case in which the power receiving unit 100 receives power alone.
  • An example of the optimal value is 3.
  • the power transmitting unit 300 periodically performs wireless communication with the power receiving unit 100 to control the transmitting power such that the receiving power of the power receiving unit 100 is not less than the lower limit of the input voltage of the DC-DC converter 210 .
  • the controller 150 measures the input voltage of the DC-DC converter 210 (Vin) (step S 1 ).
  • the input voltage Vin may be measured with the voltage detector 160 V.
  • the controller 150 determines whether the input voltage Vin is not more than the upper limit or not (step S 2 ). Information concerning the upper limit may be stored in the memory 150 M of the controller 150 in advance.
  • step S 1 If the controller 150 determines that the input voltage Vin is not more than the upper limit (S 2 :YES), the process reverts to step S 1 .
  • step S 3 If it is determined that the input voltage Vin is more than the upper limit (S 2 :NO), the controller 150 opens (turns off) all of the switch units 124 A to 124 E (step S 3 ). Because the input voltage Vin has exceeded the upper limit, step S 3 is performed to prevent the DC-DC converter 210 from being damaged.
  • the controller 150 sends data, indicating that the input voltage Vin has exceeded the upper limit, to the power transmitting unit 300 (step S 4 ).
  • the controller 150 sends data to the power transmitting unit 300 via the antenna 170 .
  • the controller 150 reads, from the memory 150 M of the controller 150 , data representing the relation between the load resistance of the DC-DC converter 210 and the receiving power of the power receiving unit 100 for each number of turns of the secondary coil 120 (step S 5 ).
  • the controller 150 determines whether the input voltage Vin can be reduced to not more than the upper limit by reducing the number of turns of the secondary coil 120 (step S 6 ).
  • the controller 150 by using data representing the relation between the receiving power P and the load resistance R, calculates the input voltage Vin (when the number of turns is less than the current number of turns), and determines whether the input voltage Vin can be reduced to not more than the upper limit by reducing the number of turns of the secondary coil 120 .
  • data representing the receiving power P may be stored in the memory 150 M of the controller 150 in advance. Further, in the memory 150 M of the controller 150 , the input voltage Vin may also be stored in advance in association with the data representing the relation between the load resistance of the DC-DC converter 210 and the receiving power of the power receiving unit 100 for each number of turns of the secondary coil 120 , as illustrated in FIG. 9 .
  • the controller 150 changes the number of turns of the secondary coil 120 such that the input voltage Vin is not more than the upper limit (step S 7 ). Specifically, the controller 150 changes the on/off state of the switch units 124 A to 124 E in the switch 124 to change the number of turns of the secondary coil 120 .
  • the controller 150 may select one of the number of turns of the winding of the secondary coil 120 satisfying a condition such that the load resistance of the DC-DC converter 210 at the receiving power P is higher than a load resistance when the electric power received from the primary resonant coil is maximum.
  • the controller 150 sends, to the power transmitting unit 300 , data indicating that the number of turns has been changed (step S 8 ).
  • This data includes the number of decreased turns, or the number of increased turns.
  • the controller 150 determines whether charging is completed or not (step S 9 ). The controller 150 determines whether charging is completed or not by determining if the battery 220 is fully charged, based on the state of charge of the battery 220 .
  • step S 9 If the controller 150 determines that charging has not been completed (S 9 :NO), the process reverts to step S 1 .
  • the controller 150 terminates the process (END). After terminating the process, the power receiving unit 100 no longer performs charging.
  • the controller 150 terminates the process (END).
  • FIG. 11 is a flowchart describing the process performed by the controller 310 in the power transmitting unit 300 .
  • the controller 310 determines whether the number of turns of the secondary coil 120 in every power receiving unit 100 has been changed from the optimal value or not (step S 11 ). As the power transmitting unit 300 receives, from each of the power receiving units 100 , the data indicating that the number of turns has been changed, the power transmitting unit 300 can recognize whether the number of turns has been changed from the optimal value or not.
  • the controller 310 reduces the transmitting power (step S 12 ).
  • An amount of power to be reduced at step S 12 is determined in advance. Accordingly, when reducing the transmitting power, a predetermined amount of power is reduced.
  • the controller 310 determines whether the input voltage of the DC-DC converter 210 (Vin) in every power receiving unit 100 is not less than the lower limit or not (step S 13 ). The controller 310 performs the determination by receiving information from each of the power receiving units 100 .
  • the controller 310 determines whether there is a power receiving unit 100 having a secondary coil 120 whose number of turns can be returned toward the optimal number (step S 14 ).
  • the controller 310 may make an inquiry to the power receiving unit 100 through data communication to cause the power receiving unit 100 to perform determination similar to step S 6 . After performing the determination similar to step S 6 , the power receiving unit 100 sends a determination result to the power transmitting unit 300 , and the controller 310 may perform the determination at step S 14 based on the determination result.
  • the controller 310 may maintain data representing the relation between the load resistance of the DC-DC converter 210 and the receiving power of the power receiving unit 100 for each number of turns of the secondary coil 120 , as illustrated in FIG. 8 or FIG. 9 , in the internal memory of the controller 310 .
  • the controller 310 itself may perform the determination similar to step S 6 without making an inquiry to the power receiving unit 100 , to perform step S 14 .
  • the controller 310 sends, to the power receiving unit 100 having a secondary coil 120 whose number of turns can be returned toward the optimal number, an instruction to return by a certain number of turns (step S 15 ).
  • the power receiving unit 100 having received the instruction returns the number of turns of the secondary coil 120 by 1 toward the optimal number.
  • the controller 310 determines whether a power receiving unit 100 whose input voltage of the DC-DC converter 210 (Vin) is higher than the upper limit exist (step S 16 ). As the power transmitting unit 300 receives, from each of the power receiving units 100 , the data indicating that the input voltage Vin has exceeded the upper limit, the power transmitting unit 300 can make the determination based on whether the data is received or not.
  • the controller 310 stops transmitting power (END).
  • step S 11 If the controller 310 determines that no power receiving unit 100 whose input voltage of the DC-DC converter 210 (Vin) is higher than the upper limit exists (S 16 :NO), the process reverts to step S 11 to repeat the process from step 11 again.
  • step S 14 determines at step S 14 that there is no power receiving unit 100 having a secondary coil 120 whose number of turns can be returned toward the optimal number (S 14 :NO)
  • the process reverts to step S 12 to reduce the transmitting power.
  • step S 17 the controller 310 restores the transmitting power to a state before step S 12 is executed (step S 17 ).
  • step S 11 the controller 310 repeats step S 11 to wait until the number of turns of the secondary coil 120 in every power receiving unit 100 has been changed.
  • the process performed by the controller 310 is described as above.
  • the power receiving unit 100 changes the on/off state of the switch 124 to reduce the number of turns.
  • an output voltage of the secondary coil 120 decreases. Accordingly, the load resistance of the DC-DC converter 210 as seen by the input terminals 211 A and 211 B is reduced and the input voltage of the DC-DC converter 210 (Vin) can be reduced. Therefore, an effective power transmission can be realized between the power receiving unit 100 and the power transmitting unit 300 without exceeding the input voltage of the DC-DC converter 210 (Vin).
  • the power receiving unit 100 capable of performing an effective power transmission with the power transmitting unit 300 , the power transmission system, and the method of controlling the power receiving unit can be provided.
  • FIGS. 12 and 13 are diagrams illustrating a structure of a secondary coil 120 X according to a modified example of the above embodiment. As illustrated in FIG. 12 , the secondary coil 120 X is configured by replacing the terminals 123 A to 123 D of the secondary coil 120 illustrated in FIG. 4 with a switch 123 X.
  • the switch 123 X includes terminals 123 XA 1 , 123 XB 1 , 123 XC 1 , 123 XD 1 , 123 XA 2 , 123 XB 2 , 123 XC 2 , and 123 XD 2 .
  • Each of the terminals is connectable to other terminals adjacent in a circumference direction or a radial direction of the secondary coil 120 X. Note that the terminals 123 XA 1 to 123 XD 1 are respectively located at the same positions as positions of the terminals 123 A to 123 D in FIG. 4 .
  • the terminals 123 XA 2 to 123 XD 2 are respectively arranged at positions adjacent to the right sides of the terminals 123 XA 1 to 123 XD 1 along the secondary coil 120 X that is coiled spirally.
  • the terminals 123 XA 2 to 123 XD 2 are respectively connectable to the terminals 123 XA 1 to 123 XD 1 . Also, each of the terminals 123 XA 2 to 123 XD 2 is connectable to other terminals adjacent in the radial direction of the secondary coil 120 X.
  • a 3-turn coil spanning from the terminal 121 A to the terminal 123 XC 2 is obtained.
  • a range from the terminal 121 A to the terminal 123 XC 2 is illustrated as a solid line
  • a range from the terminal 123 XC 1 to the terminal 121 B is illustrated as a dashed line.
  • the obtained coil is a 3-turn coil, and a pitch of the winding is equal to a pitch of adjacent windings of the secondary coil 120 X.
  • this type of pitch is referred to as “pitch-1”.
  • the terminal 123 XA 2 is connected to the terminal 123 XB 2
  • the terminal 123 XB 1 is connected to the terminal 123 XB 2
  • the terminal 123 XC 2 is connected to the terminal 123 XD 2
  • the terminal 123 XD 1 is connected to the terminal 123 XD 2
  • the switch unit 124 E is closed (is turned on), a coil spanning from the terminal 121 A to the terminal 121 B is obtained.
  • a conductive path of the coil includes a path starting from the terminal 121 A to the terminal 123 XA 2 along the winding of the secondary coil 120 X, a path from the terminal 123 XA 2 to the terminal 123 XB 2 , a path from the terminal 123 XB 2 to the terminal 123 XC 2 along the winding of the secondary coil 120 X, a path from the terminal 123 XC 2 to the terminal 123 XD 2 , and a path from the terminal 123 XD 2 to the terminal 121 B along the winding of the secondary coil 120 X.
  • a range included in the obtained coil is illustrated as a solid line, and a range not included in the obtained coil is illustrated as a dashed line.
  • the input voltage of the DC-DC converter 210 can also be changed similarly to the secondary coil 120 illustrated in FIG. 4 or FIG. 5 .
  • the receiving power of the power receiving unit 100 is determined depending on a rated output of the battery 220 . However, if a rated output of the battery 220 is not determined, the receiving power of the power receiving unit 100 may be measured.
  • a power receiving unit 100 Y illustrated in FIG. 14 for example a wattmeter 120 Y for measuring receiving power by detecting a voltage and a current of the secondary coil 120 may be installed to the secondary coil 120 .
  • the power receiving unit 100 Y may be configured such that data representing the receiving power measured by the wattmeter 120 Y is output to the controller 150 and that the controller 150 changes the number of turns based on the data representing the receiving power input from the wattmeter 120 Y.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Charge And Discharge Circuits For Batteries Or The Like (AREA)
  • Coils Or Transformers For Communication (AREA)
US15/902,395 2017-03-29 2018-02-22 Power receiving unit, power transmission system, and method of controlling the power receiving unit Active 2039-07-19 US11070086B2 (en)

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